The invention relates to a syringe and a syringe family for use with a metering device and to a metering device for use with a syringe or a syringe family.
Pipettes are metering devices for measuring out and transferring liquids. They are frequently designed as repeater pipette or multipipettes, which are used together with a syringe, in order to draw liquid into the syringe and gradually to discharge said liquid therefrom. A repeater pipette is known from DE 29 26 691 C2, the entire contents of which is incorporated herein by reference, and U.S. Pat. No. 4,406,170, the entire contents of which is incorporated herein by reference, which, in particular, discloses the repeating mechanism of the repeater pipette. It also discloses the fixing of the syringe to the repeater pipette. To this end, the syringe has a syringe flange which may be inserted from the side into a substantially U-shaped groove of the pipette, which is open at the side. An axial pressure spring secures the inserted syringe flange in the groove. For connecting the syringe piston to a piston adjusting device of the pipette, an insertion element is present which receives an end portion of the syringe piston between two jaws. The jaws are able to be pressed against the syringe piston by means of a flap-shaped clamping member, the actuating lever thereof protruding from the housing through an opening. This manner of fixing the syringe has the drawback that the syringe has to be handled for insertion and coupling to the piston adjusting device and/or for uncoupling and removal.
DE 43 41 229 C2, the entire contents of which is incorporated herein by reference, and U.S. Pat. No. 5,620,660, the entire contents of which is incorporated herein by reference, propose a pipette system which is more suitable for manual actuation with a syringe which may simply be inserted axially into the pipette and/or may be removed therefrom. This pipette system has a syringe comprising a fastening portion and a syringe piston, and a pipette which comprises in a pipette housing a receiver for the fastening portion and a receiving body with a piston receiver for the syringe piston and/or a piston rod connected thereto. In addition, fastening devices are present for the reversible and/or releasable fixing of the fastening portion and syringe piston in the receivers and piston adjusting devices are present for displacing the receiving body in the pipette housing. The fastening portion and the syringe piston are able to be pushed into their fastening positions through axial openings in their receivers.
The fastening devices have gripping devices which may be positioned radially for fixing the fastening portion and the syringe piston in the fastening positions. The gripping devices have syringe gripping levers mounted pivotably in the pipette housing and piston gripping levers mounted pivotably in the receiving body. The syringe gripping levers and the piston gripping levers are designed to be double-armed with a gripping arm and an actuating arm, the syringe gripping levers comprising contact points on the inner faces of their actuating arms, which by the actuation of their actuating arms are able to be pivoted externally against the actuating arms of the piston gripping levers and actuate the piston gripping levers.
As a result, it is achieved that the syringe and the pipette are able to be connected to one another by a purely axial relative movement and are able to be separated from one another by actuating the actuating arms. According to one embodiment, the fastening portion is a syringe flange and according to a further embodiment the syringe piston has a piston flange for engaging behind the gripping devices.
From DE 10 2005 023 203, the entire contents of which is incorporated herein by reference, and US 2006263261 A1, the entire contents of which is incorporated herein by reference, an embodiment of the pipette according to DE 43 41 229 C2, the entire contents of which is incorporated herein by reference, is known in which the syringe may be released from the pipette by the actuation of just one actuator.
The commercial Multipette® (plus/stream/X-stream) embodiments of this metering system from Eppendorf AG comprise Combitips® (plus) syringes, which have a cylinder with a piston movement area on the inside and a syringe flange at the upper end of the cylinder. The syringes are supplied with various filling volumes (0.1 ml, 0.2 ml, 0.5 ml, 1 ml, 2.5 ml, 5 ml and 10 ml). The internal diameter of the piston movement area is dimensioned so that the filling volume is received into the syringe and/or discharged therefrom with a maximum piston adjusting path of the Multipette® of Eppendorf AG of 50 mm plus an over-stroke of a few millimeters. In the syringe with a nominal volume of 10 ml accordingly the internal diameter of the piston movement area is 15.96 mm With smaller syringes, the internal diameter of the piston movement area is correspondingly smaller. The cylinders of the smaller syringes have at the upper end of the piston movement area a cylindrical widening, the internal diameter thereof being in each case markedly smaller than 15.96 mm and which is all the smaller, the smaller the filling volume of the syringe. One reason for the cylindrical widening is that, as a result, a depth stop of the piston may be produced in the cylinder, whereby damage to the piston sealing lip is prevented from occurring by positioning the sealing lip on the lower front face of the cylinder. A further reason is that in the small syringes, the piston area below the coupling piece inserted into the metering system is designed to be thicker, in particular is designed as a wing piece, in order to achieve as a result an increase in the resistance to buckling of the piston rod in the stored state.
Proceeding from the flange, the cylinders have on the periphery four axially extended ribs protruding outwardly, which are distributed uniformly over the periphery. The ribs have at the bottom one respective shoulder for supporting on the edge of holes of a tray or a box. So that syringes of different filling volumes may be inserted into uniform holes of a tray or a box, the shoulders of syringes which have different filling volumes are the same distance from the axis of the cylinder.
The known metering system permits accurate metering with low measurement deviation.
Proceeding therefrom, the object of the invention is to provide a syringe and a syringe family for use with a metering device and a metering device for use with a syringe or a syringe family which permit even more accurate metering.
The object is achieved by a syringe having the features of Claim 1.
A syringe according to the invention for use with a metering device comprising a centering element with an axial through-passage in a receiver for a syringe cylinder and an axially displaceable piston receiver for a syringe piston has    a syringe cylinder    and a syringe piston,    the syringe cylinder comprising an outlet at the bottom,    a centering flange at the top on the external periphery for inserting into the receiver,    a cylindrical piston movement area connected to the outlet, with a first internal diameter, in which the syringe piston is sealingly guided, and    at least at a distance of at least 3 mm from the upper end of the syringe cylinder a centering region for inserting the centering element, which has a second internal diameter which exceeds the first internal diameter and is at least 16.2 mm and at most 17.7 mm,    and the syringe piston at the upper end has a coupling piece for inserting into the piston receiver.
The syringe family according to the invention for use with a metering device comprising a centering element with an axial through-passage in a receiver for a syringe cylinder and an axially displaceable piston receiver for a syringe piston comprises    a plurality of syringes with different filling volumes, in each case comprising    a syringe cylinder    and a syringe piston,    the syringe cylinder comprising an outlet at the bottom,    a centering flange at the top on the external periphery for inserting into the receiver,    a cylindrical piston movement area connected to the outlet in which the syringe piston is sealingly guided, and    at least at a distance of at least 3 mm from the upper end of the syringe cylinder a centering region for inserting the centering element,    the syringe piston at the upper end comprising a coupling piece for inserting into the piston receiver    and the centering regions of the syringes with different filling volumes having a matching contour on the inside.
The plurality of syringes are preferably selected from the group of syringes which have filling volumes of 10 ml, 5 ml, 2.5 ml, 1 ml, 0.5 ml, 0.2 ml and 0.1 ml.
The centering regions of the syringes which have different filling volumes have a matching contour. By “matching contour” in the centering region is understood the same and/or different geometries, which are tailored to the same predetermined centering contour. The syringes which have a matching contour are, therefore, suitable for cooperating with one and the same centering element of the metering system which has the centering contour.
The metering device according to the invention for use with a syringe comprising a syringe cylinder and a syringe piston, the syringe cylinder comprising an outlet at the bottom, a centering flange at the top on the external periphery, a cylindrical piston movement area connected to the outlet, in which the syringe piston is sealingly guided, and further above a centering region and a coupling piece at the upper end of the syringe piston or for use with a syringe family comprising a plurality of such syringes, has    a housing comprising    a receiver for the centering flange of the syringe cylinder with an axial opening for axially inserting the centering flange into a fastening position,    a centering element arranged in the receiver, aligned with the axial opening, with an axial through-passage for axially inserting the syringe cylinder into the centering region,    a receiving body with a piston receiver for axially inserting the coupling piece into a fastening position,    fastening devices for releasably holding the centering flange and coupling piece in their fastening positions in the receiver and in the piston receiver,    the fastening devices comprising radially positionable gripping devices for gripping the centering flange and the coupling piece in the fastening positions,    and piston adjusting devices for displacing the receiving body in the housing.
The terms “at the top” and “at the bottom” refer to the preferred alignment of the syringe when metering, in which the syringe is held vertically with the outlet at the bottom and the centering flange at the top.
The metering device may, in particular, be a manipulable and/or stationary metering device, driven manually and/or by motor. It may, in particular, be a pipette, a repeater pipette, dispenser, metering station or automatic metering device. Preferably, it is a dispenser.
The syringe according to the invention is able to be fixed easily to a metering device according to the invention in a reversible manner To this end, the syringe is inserted in the axial direction into the metering device, the centering flange being gripped by means of radially positionable gripping devices for gripping the centering flange in the receiver of the metering device and the syringe piston being gripped on its coupling piece in the piston receiver by radially positionable gripping devices for gripping the piston rod. The gripping of the centering flange and of the coupling piece by the gripping devices may be controlled by the axial insertion of the syringe in the receiver of the metering device. To this end, the metering device may be designed as disclosed in DE 43 41 229 C2, the entire contents of which is incorporated herein by reference, and U.S. Pat. No. 5,620,660, the entire contents of which is incorporated herein by reference. The embodiments relative thereto of the aforementioned patents are incorporated in the present application.
When inserting the syringe into the metering device the centering element axially penetrates the centering region and bears radially against the inside of the centering region. The dimensions and geometries of the centering element and of the centering region are tailored to one another, so that the syringe cylinder is centred by the inserted centering element. As a result, the syringe cylinder with the centering region is guided accurately into the receiver so that it may be gripped easily and securely by the gripping devices.
By the bearing of the centering region on the centering element, a deformation in the centering region of the syringe cylinder may be corrected. In particular, the centering element may correct a non-circular shape of the syringe cylinder to form an ideal circular shape. As the centering region is either located in the immediate vicinity of the piston movement area, which is crucial for accurate metering, or in the immediate vicinity of the transition region, which counteracts damage to the sealing lip of the piston, the correction in the centering region acts positively on the metering accuracy. A non-circular cylinder has a cross-sectional area which is different from the circular cylinder, which leads to metering errors. In particular, by the circular shape the tightness of the seal of the syringe piston in the cylinder and thus the accuracy of the metering is improved. A non-circular syringe cylinder, due to the altered cross-sectional area, also has the result that, in particular, at the end of the receiving stroke and during the initial discharge strokes air flows past the syringe piston and a small volume of liquid is received and/or discharged. This drawback is overcome by the invention.
In addition, the guidance of the centering region on the centering element prevents faulty alignment of the syringe relative to the metering device and tilting of the syringe relative to the metering device under load. A faulty alignment may occur with a conventional metering system, when the syringe is gripped in tilted alignment by the gripping devices of the metering system. Tilting under load may occur with a conventional metering system if, during metering, the syringe in the vicinity of its outlet touches a wall with a contact force. This type of discharge is denoted as wall discharge. In particular, it is used with small discharge volumes in order to avoid errors by uneven drop break from the syringe. As a result, the syringe cylinder is pivoted relative to the syringe piston, whereby liquid is displaced and a metering error may result. Additionally, reduced tightness of the seal of the piston in the tilted syringe cylinder may impair the accuracy of the metering. These disadvantageous features of the previously known syringe and metering devices are also overcome by the present invention.
For centering the syringe, it is important that the centering element bears against the centering region at a distance from the upper end of the syringe cylinder. Only when the centering element engages correspondingly deeply in the syringe piston, is it able to bear all around the centering region and correct a non-circular shape of the syringe cylinder, align and support it and thus prevent tilting. The stiffening of the syringe cylinder by the centering flange at the upper end of the syringe works against the correction of a non-circular cross section in the piston movement area. Thus the second internal diameter of at least 16.2 mm of the centering region of the syringe according to the invention and/or the centering region of the syringes of the syringe family according to the invention is present at least at a distance of at least 3 mm from the upper end of the syringe cylinder, i.e. in the immediate vicinity of the piston movement area and/or the transition region. The centering region is thus also characterized by its immediate vicinity to the piston movement area.
The syringe piston may be inserted with its coupling piece through the axial through-passage of the centering element, so that the syringe piston may be pulled out of the syringe cylinder. Optionally, the piston receiver engages in the axial through-passage of the centering element for coupling the coupling piece.
The internal diameter in the centering region of at least 16.2 mm ensures that syringes with a filling volume of up to 10 ml with an internal diameter of the piston movement area of up to 15.96 mm may be inserted into a metering device with a maximum piston adjusting path of 50 mm, plus an over-stroke of a few millimeters. Thus syringes of all current filling volumes are covered by the invention. Larger filling volumes (for example 25-50 ml) are possible when an adapter is used, which reduces the larger diameter of the syringe cylinder to the smaller diameter of the receiver of the metering device. An adapter is useful, even with small-volumed syringes, as it facilitates the ability of small syringes to be grasped and handled. Preferably, the adapter has the centering region. As a result, the adapter is also centred in the metering device and thus aligns the syringe, supports it and prevents tilting of the syringe, in particular during wall discharge.
The invention includes syringes in which the syringe cylinder is in one piece. In addition, the invention includes syringes in which the syringe cylinder is in several parts. In particular, the invention includes syringes in which the syringe cylinder has the piston movement area and the outlet on a lower part and the centering flange and the centering region on an upper part, which may be connected to the lower part, for example by means of a bayonet, screw and/or snap connection. The upper part may, in particular, be an adapter.
The internal diameter of the centering region of the syringe according to the invention exceeds the internal diameter of the piston movement area, so that during injection-moulding the syringe cylinder may be filled more evenly with plastics material and thus made more dimensionally stable. The step change of the internal diameter between the piston movement area and the centering region namely produces a flow brake, which preferably forces the hot plastics mass injected below the centering region to fill initially the lower part of the syringe cylinder and thus the piston movement area uniformly and subsequently the centering region and the centering flange. As a result, the dimensional stability of the syringe cylinder in the piston movement area and thus the accuracy of the metering are improved.
Moreover, a step change in the internal diameter between the piston movement area and the centering region makes it possible for the syringe piston which is fully inserted into the syringe cylinder to be guided at the top in the piston movement area, when the syringe is not connected to the metering device. To this end, the external diameter of a guide region of the syringe piston arranged below the coupling piece may approximately correspond to the internal diameter of the piston movement area. The external diameter of the guide region should be less than the internal diameter of the piston movement area by at least the sum of the tolerances of the syringe piston (for example 0.1 mm) and the syringe cylinder (for example 0.1 mm). Due to the larger internal diameter in the centering region, a gap remains between the syringe piston and the centering region, into which the centering element may be inserted. Thus by the widening of the internal diameter in the centering region relative to the internal diameter in the piston movement area a centering of the syringe piston in the syringe is ensured, when the syringe is connected to the metering device and the centering element engages in the widened centering region and fills said region. The centering and guiding of the syringe piston in the syringe separated from the metering device is provided in spite of the widened centering region, as the guide region of the fully inserted syringe piston bears against the piston movement area and is guided, and/or in syringes with small volumes (for example 1 ml and below) against the transition region.
The centering of the syringe piston by the guide region in the syringe separated from the metering device avoids tilting of the syringe piston in the syringe cylinder and thus deformation in the sealing region of the syringe piston and/or the syringe cylinder by partial irreversible widening, whereby metering errors are avoided.
The guiding of the syringe piston at the top in the piston movement area may be effected by wings of the syringe piston protruding outwardly and extending axially and/or by a disc below the coupling piece of the syringe piston. The disc may additionally effect a covering of the piston movement area, which prevents penetration of dirt into the syringe cylinder, which may impair the seal of the piston and/or may contaminate the liquid to be metered.
In addition, the step change in the internal diameter between the centering region and the piston movement area permits tolerances to be monitored in a simple manner by means of force measurement when the syringe piston and the syringe cylinder are joined together during manufacture. If the diameter of the syringe piston is too large, two force increases are measured during the joining process, namely when the syringe piston penetrates the centering region with its sealing region and then when the sealing region penetrates the piston movement area. If the diameter of the piston does not exceed the tolerance upper limit, a force increase is only measured when the sealing region penetrates the piston movement area. By simple and clear measurement, it may thus be established whether the diameter of the syringe piston exceeds the tolerance upper limit and the syringe piston has to be discarded. It is particularly important to monitor that the tolerance upper limit has been maintained, as non-circularity of the syringe piston may be established as an enlargement of the diameter. The use of syringe pistons which, due to a non-circular sealing region, cause metering errors, may thus be avoided. As the tolerances of the syringe piston and the syringe cylinder are tested, when the tolerance upper limit is exceeded preferably the entire syringe is discarded. The present invention, therefore, also comprises a method for testing the tolerances.